Chain tensioner necessary?

[2door]

If you think for a moment that you well ever submit a chain to the kind of stress that it was designed for, and I'm talking about industrial roller chain, with the forces available from a motorized bicycle, you have another think coming.
"Pre-Stretched" ??? I've never seen this term applied to any roller chain from any manufacturer. "Pre-Stressed". Possibly, and the forces used are far more than you'll ever see in our applications.
As I've said, the kit supplied chains, typically #415 chains have some limitations and short-comings when compared with a chain manufactured by Morse, Browning, or any of several other American made industrial roller chains.
I'll stand by my original statement. Roller chains do not "stretch", they wear.

Personally I have a number of kit chains stored under my work bench because I don't use them. I install a good quality #41 industrial roller chain on all of my builds. I never experience chain problems associated with some of the kit chain. And contrary to what I've seen posted here, #415 and #41 are not compatible in terms of master or half links. The pin sizes are different which does not allow matching one to the other.

Tom

 

[nightcruiser]

From Diamond Chain's FAQ section:

"What is meant by "pre-stretching" or "pre-loading" roller chain, why is it done, and is it important?
Following assembly, an initial load is applied to the chain, which is called a pre-load. This loading approximates the recommended maximum loading in service and is done to align the various chain components such as pins, bushings, and link plates. The benefit of pre-loading is that it helps greatly eliminate the initial elongation often found in "lesser" chains. Elimination of this initial elongation can increase the chains useable service life therefore pre-loading is very important. Diamond Chain Company pre-loads every standard and heavy series chain it manufacturers."

http://www.diamondchain.com/frequently-asked-questions.php

IMHO elongation=stretching.

 

[2door]

Isn't that exactly what I said?

Tom

 

[nightcruiser]

Isn't that exactly what I said?

Tom

You said "Chains don't stretch."

I said China KIT chains DO stretch because they are not pre-stretched/stressed like a quality chain. As the FAQ indicates, a freshly manufactured chain will elongate/stretch when stressed for the first time, and that is why a quality industrial chain is pre-stressed. A China kit chain is FAR from an industrial chain and they go through all sorts of changes when they encounter the stress from the motor. Trust me, I witnessed the death of two kit chains, they are definitely the "lesser chains" that will elongate/stretch when stressed... My #41 chain has been rock solid though, and I suspect it will out last several ht motors and serve for at least 4000-5000 miles at a minimum...

 

[MitchP]

I lubed my chain last night (1st lube, silicone). Then, this morning, it was quite slack. I didn't realize it until it bunched up in the crank case. SOMETHING happened. I could hardly tension it until I moved the wheel back. So yes some sort elongation occurs.

 

[rudyauction509]

chains stretch/wear/whatever you want to call it because as the pins and bushings wear, they become loose because the pins become thinner and the bushings wider, by a tiny amount. this allows the chain links to move apart a tiny bit. No chain under normal conditions stretches like a rubber band because metal isn't rubber, though they do get longer because of the pin/bushing wear. Does that make sense?